A sinkhole that swallowed a Florida man when it collapsed the bedroom portion of his home overnight is "extremely unstable," expected to grow bigger and too dangerous for rescuers to approach, Hillsborough County officials said.

"Until we know where it's safe to bring the equipment, we really are just handicapped and paralyzed and can't really do a whole lot more than sit and wait," Hillsborough County Fire Chief Ron Rogers told reporters this evening. "It's a tough situation; it's even tougher for the family."

The hole that pulled in Jeff Bush, 36, opened up at around 11 p.m. Thursday night in Seffner, Fla., authorities said.

"[Family members] heard a sound that they described as a car crash emanating from the bedroom in the back of the house," Rogers said at an earlier news conference.

The hole remained 20 to 30 feet wide this evening, officials said, but it had progressively deepened beyond the 20 feet seen earlier today.

"The soil cannot hold the slope that it is right now," said Larry Madrid, president of Madrid Engineering Group, a sinkhole expert called in by the county.

Engineers feared a further sudden collapse because the house sat on fluid, sandy soil, and they remained uncertain about where the unstable area ended.

"[Another collapse] could happen now, it could happen days from now," Madrid said. "It could happen slowly, it could happen quickly."

The partially collapsed house and two neighboring houses have been evacuated.

"As items fall in from the house, [they] get pulled down in," said Bill Bracken, an engineer working with Hillsborough County Search and Rescue.

"Given the size of the hole, I cannot tell you why [the whole house] hasn't collapsed yet," he said.

The instability meant rescuers were unable to continue searching for Jeff Bush within the house.

"As I told the family earlier, the only thing that would be worse than what they're feeling now for their loss would be to experience additional human loss," Hillsborough County Administrator Mike Merrill said this evening. "That's the dilemma and the dilemma is a very painful dilemma for everyone."

"This is not your typical sinkhole," he added. "This is a chasm that covers a great distance. They still have not been able to find the boundaries of the underground chasm."

After the initial collapse, Jeff Bush's brother Jeremy jumped into the sinkhole and tried to rescue him, only to need rescuing himself.

"I jumped in the hole and was trying to dig him out, but I couldn't find him," Jeremy Bush tearfully told WFTS. "I thought I could hear him hollering for me to help him.

"I didn't see any part of him when I went in there," he said. "All I seen was his bed and I told my father-in-law to grab a shovel so I could start digging, and I just started digging and started digging, and the cops showed up and pulled me out of the hole and said the floor was still falling in."

A first responder "heroically" jumped in and rescued Jeremy Bush, Rogers said.

"I went to the bedroom and saw the sinkhole taking the entire bedroom," Hillsborough County Deputy Douglas Duvall said in a video taken and posted by the sheriff's office online.

"I looked down. There was a family member inside the hole that was trying to get the victim out," Duvall said. "I reached out and was able to get him by his hand and pull him out of the hole. The hole was collapsing. At that time, we left the house."

This evening Duvall added, "I've never seen anything like it. I've never seen anything move so fast and do so much devastation.

"If you guys know this neighborhood, this family, pray for them," he said. "They need it."

The family was evacuated from the home as rescuers tried to get to the man. Listening devices and cameras were sent into the hole.

"They did not detect any signs of life," Rogers said. "There continued to be collapses of the earth below the floor to the point where they had to eventually back out of the house."

When asked what authorities believe the victim's status is, Rogers said earlier today, "Until we can actually determine where the victim is, I can't really answer that. We're going to do everything we can for Mr. Bush, but we have to make sure we don't endanger other personnel in the process."

Jeremy Bush was trying to be hopeful, but said he feared the worst.

When asked by WFTS why the family was staying nearby, Bush tearfully said, "Just to get closure, I guess, make sure he's not dead, see if he's alive. But I know in my heart he's dead. I just want to be here for him because I love him. He's my brother, man."